It is often important to maintain low-humidity environments in various synthesis or manufacturing processes. For instance, successful in-situ synthesis of biopolymer “biochips” or arrays/micorarrays may require an anhydrous, or substantially humidity-free environment, e.g., where the biopolymer ligands of the array are “grown” in situ using chemical synthesis protocols that produce the ligands through stepwise addition of activated monomers. Water concentrations in such an environment sometimes need to be as low as 1 PPMv (e.g., in laying-down protein or DNA microarrays).
In order to maintain a production environment in an anhydrous or near-anydrous state—adjusting conditions or terminating activity if environmental conditions pass beyond acceptible limits—accurate monitoring is required. Typically, in response to sensor readings indicating higher humidity levels, the production environment is “blown-out” with dry gas, such as N2 gas. This purges unwanted moisture from the synthesis area.
To maintain extremly low water vapor concentrations, measurements are typically taken using a capacitance-type sensor. In a capacitance or dew point sensor, water vapor absorbed or desorbed by a porous layer alters the layer's capacitance. This alteration is measured using adjacent conductive members in order to provide a humidity reading.
In such a sensor, water is absorbed much more quickly than it is desorbed. Accordingly, it has been appreciated that quicker response time may be achieved in taking humidity measurements using a dry sensor than one that has already been saturated. A dewpoint meter produced by Xentaur (Medford, N.Y.: Model—XPDM), capitalizes on this feature by isolating a sensor in a region filled with dessicant until it is withdrawn therefrom and exposed in another region to sample gas.
The present invention, likewise, uses an isolated sensor approach. However, an improved manner of sensor drying and/or maintaining a sensor in a dry state is taught herein. Instead of requiring a complex apparatus including multiple chambers and perishible dessicants like the referenced system, a more elegant system is described. In addition to such advantages as increased reliability, ease of operation and maintenance, and cost or space savings, variations of the inventive system offer further possible advantages that may be apparent to those skilled in the art.